1. Field of the Invention
The present invention relates to technology for managing contents stored on portable recording media and distributed to users.
2. Related Art
One method of delivering contents to users is to distribute contents stored on recording media. Since there is a possibility of contents stored on recording media and delivered to users being played and copied indiscriminately, the improper use of contents needs to be prevented.
As technology that prevents the improper use of contents, unexamined Japanese patent application publication no. 2002-41482 discloses technology in which an encrypted content and a computer program (hereinafter, simply “program”) are stored on a recording medium, decryption information for decrypting the encrypted content is managed by a center, and the decryption information is acquired from the center by running the program.
Furthermore, in unexamined Japanese patent application publication no. 2000-200229 is disclosed technology for storing rights information showing an allowable number of content playback and the like on a recording medium together with both an encrypted content generated by encrypting a content and a decryption key for decrypting the encrypted content, and decrypting and playing the content using the decryption key, in compliance with the rights information.
On the other hand, there are those who want to manage the disclosure of contents, such as, for example, being able to set the release period of a content and permit the use of the content in accordance with the release period, after a recording medium that stores the content has been predistributed. However, the above technology is not able to meet demands such as this.